The present disclosure relates to a sound reproduction device having a noise cancelling function.
Earphone devices with a noise cancelling function (hereinafter, also referred to as NC earphone devices) have come into wide use. Because an NC earphone device performs noise cancelling processing by itself, users may enjoy a noise cancelling effect even when the NC earphone device is connected to a normal audio player.
FIG. 13 is a diagram showing an appearance of the NC earphone device 100 according to related art. The NC earphone device 100 shown in FIG. 13 is a so-called ear-hole insertion type of earphone device. Here, the ear-hole insertion type of earphone device includes any earphone device of which sound output units are inserted into user's ear-holes so that the users may hear. For example, the ear-hole insertion type of earphone device is an in-ear type of earphone device or a canal type of earphone device. The NC earphone device 100 shown in FIG. 13 is the canal type of NC earphone device.
As illustrated in FIG. 13, the NC device earphone 100 has a left channel (Lch) output unit 101L, a right channel (Rch) output unit 101R, a plug unit 102, and a cord housing unit 103. A cord connects the plug unit 102 to the cord housing unit 103, and each cord connects the Lch output unit 101L and the Rch output unit 101R to the cord housing unit 103, as illustrated in FIG. 13.
A driver unit outputting sounds corresponding to sound signals input from the plug unit 102 and a microphone recording external sounds for the realization of the noise cancelling function are installed in the Lch output unit 101L and the Rch output unit 101R, respectively.
An electric circuit unit (a noise cancelling processing unit) to provide the noise cancelling function is installed inside of the cord housing unit 103. The noise cancelling processing unit generates a noise cancelling signal of the left channel based on a Lch sound signal input from the plug unit 102 and a sound signal recorded from the microphone of the Lch output unit 101L and a noise cancelling signal of the right channel based on a Rch sound signal input from the plug unit 102 and a sound signal recorded from the microphone of the Rch output unit 101R. When the noise cancelling processing unit drives the driver unit of the Lch output unit 101L according to the noise cancelling signal of the left channel and the driver unit of the Rch output unit 101R according to the noise cancelling signal of the right channel, users wearing the NC earphone device 100 may hear noise-cancelled sounds.
In addition, the cord housing unit 103 has a battery case 103A which accommodates a battery to supply electric power that are used to process the above mentioned noise cancelling.